4.2 Problem Solving: Hand-Tracing Hand-tracing is a simulation of code execution
ID: 3745034 • Letter: 4
Question
4.2 Problem Solving: Hand-Tracing Hand-tracing is a simulation of code execution in which you step through instructions and track the values of the variables. In Programming Tip 3.6, you learned about the method of hand-tracing. When you hand-trace code or pseudocode, you write the names of the variables on a sheet of paper, mentally execute each step of the code and update the variables. It is best to have the code written or printed on a sheet of paper. Use a marker, such as a paper clip, to mark the current line. Whenever a variable changes, cross out the old value and write the new value below. When a program produces output, also write down the output in another column. Consider this example. What value is displayed? int n 1729; int sum = 0; while (n > ) int digit n % 10; sumsum digit; n n10; coutExplanation / Answer
Answer are as follows
Answer 1.
the tracings are as follows
n count digit
1796 0
179 1 6
17 1 9
1 2 7
0 2 1
As n becomes 0, comes out of the loop
Answer 2. It computes all the digits in n that are 6 or 7.
Answer 3. Total 5 values are printed. they are 1,2,3,5,8
Answer 4. Output of r i c is
r is Fred
i = 4
c = d
Answer 5. The program Prints the every other character in string s and also counts the number of characters in s
Answer 6.
print "Enter the string"
get s
r =""
i=0
while i < length of s
c= ith chsracter of s
r = c + r
i++
print r
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Practice It Answer
Answer 1: 8 is the last value printed
Answer2:
int result = 1;
while(n>0)
{
int digit = n%10;
result = result *digit;
n = n/10;
}
cout<<result<<endl;
Answer 3 ,4 has same solution
int main()
{
int num, rev = 0;
int rem;
cout<<"Enter Number: ";
cin>>num;
while(num!=0)
{
rem = num%10;
rev= rev*10 + rem;
num = num/10;
}
cout<<"Reverse: "<<rev;
}
Answer 5.
trace are :
n r
1 1
2 4
3 9
4
so at the end n = 4 and r = 9
Answer 6.
int n =1;
while(n<=3)
{
int r = n*n;
cout<<r;
if(n<3)
{
cout<<"," ;
}
n++;
}
Answer 7.
the Code is wrong, for the inputs that are less than ten, the loop condition should be temp>0;
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